Fe-MOR and Fe-FER as catalysts for abatement of N2O with CH4: in situ UV-vis DRS and operando FTIR study

The catalytic reduction of N2O with CH4 in absence or in presence of O2 (CRN2O or SCRN2O) and H2O (hydrothermal conditions) was studied on Fe-MOR and Fe-FER catalysts with similar Al distribution and iron-loading. In N2O decomposition and SCRN2O Fe-FER catalysts were more active than Fe-MOR, whereas in CR N2O the catalysts exhibited similar activity. In situ FTIR and UV-vis spectroscopies of thermally activated catalysts revealed that Fe(II) species are better stabilized in FER than in MOR topology. In the presence of CH4, Fe(III)-oxo species were reduced to Fe(II) in both zeolites and became active sites for the CRN2O process. In SCRN2O the presence of O2 decreased the activity of Fe-MOR due to a partial re-oxidation of the active sites. The addition of H2O to the feed caused a poor and reversible deactivation. Operando FTIR experiments provided insights into the reaction pathways and suggested formaldehyde and formate surface species as intermediates.